Breast cancer is a disease that kills over 45,000 women each year in the United States alone. Over 180,000 new cases of breast cancer are diagnosed annually and one out of eight women are estimated to develop breast cancer annually. However, the diagnosis “breast cancer” comprises a number of genetically diverse cancer cells. As a result, different breast tumors have different prognosis and respond differently to treatment regimes. For example, breast tumors expressing HER-2/neu have worse prognosis than tumors which do not express HER-2/neu. Moreover, because of known genetic instability, the gene expression pattern of the cancer cells changes during different stages of the disease, as well as in response to treatment regimens.
At the present, a pathologist classifies tumor cells according to their immunohistological patterns and using cDNA microarrays and other gene expression measuring methods, and/or by mutation detection methods, all of which are commercially available. The information is used to classify tumors and in some instances to provide prognosis for patients with the tumor. However, in only a few treatment methods is this classification of any practical use when determining treatment regimes, because the majority of the therapeutic methods currently available are non-discriminatory and directed generally against rapidly diving cells. Currently, an individual diagnosed with breast cancer may be treated with surgery, hormone therapy, chemotherapy, and/or radiation. If the patient develops metastatic disease, radiation and high dose chemotherapy are required to ablate the cancer in remote areas such as the brain, bone, and liver. The majority of therapies currently available for the treatment of breast cancer are toxic, dangerous, unspecific, costly, and many are ineffective, especially in the treatment of metastatic disease.
Therefore, while accuracy in diagnosis of specific types of breast cancer has improved significantly, only a few treatments can presently be custom-designed to meet the specific needs of an individual patient, by taking into account the differences in the expression profile, and/or mutations in the different types of cancer cells. For example, breast cancer wherein the cancer cells express increased number of estrogen receptors is responsive to treatment with extrogen receptor blockers such as Tamoxifen, whereas cancer with cells not having excessive number of estrogen receptors will not respond to such treatment.
As a result of advances in genetics, a number of genes involved in different types of breast cancer have already been identified, including BRCA1 (Online Mendelian Inheritance of Man (OMIM) #113705), BRCA2 (OMIM #600185), BRCATA (OMIM #600048), BRCA3(OMIM #605365), BWSCR1A (OMIM #602631), the TP53 gene (OMIM #191170), the BRIP1 gene (OMIM #605882), and the RB1CC1 gene (OMIM #606837) on 8q11. Mutations in the androgen receptor gene (AR; OMIM #313700) on the X chromosome have been found in cases of male breast cancer (OMIM #313700.0016). A mutation in the RAD51 gene (OMIM #179617) was found in patients with familial breast cancer (OMIM #179617.0001). The 1100delC allele of the CHEK2 gene (OMIM #604373.0001) has been shown to confer an increased susceptibility to breast cancer in women and especially in men. Further, the NCOA3 (OMIM #601937) and ZNF217 (OMIM #602967) genes, located on 20q, undergo amplification in breast cancer; when overexpressed, these genes confer cellular phenotypes consistent with a role in tumor formation (Anzick et al., Science 277: 965-968, 1997; Collins et al., Proc. Nat. Acad. Sci. 95: 8703-8708, 1998). Furthermore, the PPM1D gene (OMIM #605100) on 17q is commonly amplified in breast cancer and appears to lead to cell transformation by abrogating p53 (OMIM #191170) tumor suppressor activity (Bulavin et al., Nature Genet. 31: 210-215, 2002). Therefore, it would be advantageous to develop a treatment system which could utilize the specific information which can be obtained from the genetic and expression analysis. Moreover, it would be useful to develop a system which could additionally be adapted to treat all different types of breast cancers. Such a system would be less toxic and provide a more effective treatment than the non-specific regimes available to date.
One recent approach to the treatment of cancer is immunotherapy, which is based on the observation that human tumor cells express a variety of tumor-associated antigens (TAAs) that are not expressed or are minimally expressed in normal tissues. These antigens, which include viral tumor antigens, cellular oncogene proteins, and tissue-specific differentiation antigens, can serve as targets for the host immune system and elicit responses that result in tumor destruction. This immune response is mediated primarily by lymphocytes; T cells in general and class I MHC-restricted cytotoxic T lymphocytes in particular play a central role in tumor rejection. Unfortunately, as evidenced by the high incidence of cancer in the population, the immune response to neoplastic cells often fails to eliminate tumors. The goal of active cancer immunotherapy is to augment anti-tumor responses, particularly T cell responses, in order to more effectively result in tumor reduction.
Most attempts at active immunization against cancer antigens have utilized whole tumor cells or tumor cell fragments as immunogens. However, this approach does not afford reproducibility, or control over the precise antigens included in each immunization.
The cloning of genes encoding tumor associated antigens has opened new possibilities for the immunotherapy of cancer based on the use of recombinant or synthetic anti-cancer vaccines. Tsang et al., J. Natl. Cancer Inst. 87: 982-90 (1995); Kawakami et al., Proc. Natl. Acad. Sci. USA 91:6458-62 (1994). In recent years, much effort has been expended on “gene therapy” as a means of combating cancer. The term “gene therapy” has been used to describe a wide variety of methods using recombinant biotechnology techniques to deliver a variety of different materials to a cell. Such methods include, for example, the delivery of a gene, antisense RNA, a cytotoxic agent, etc., by a vector to a mammalian cell, preferably a human cell either in vivo or ex vivo. Most of the initial work has focused on the use of retroviral vectors to transform these cells. This focus has resulted from the ability of retroviruses to infect cells and have their genetic material integrated into the host cell with high efficiency. The retroviral vector is typically a modified virus such as Moloney Murine Leukemia Virus (MMLV), which has had its packaging sequences deleted to prevent packaging of the entire retroviral genome.
However, numerous difficulties with retroviruses have been reported. One problem that has developed was initially seen as a key advantage of retroviruses, mainly their ability to integrate into the chromosome. However, such integration can be problematic, depending on the chromosomal site of viral insertion. A number of other viruses that were initially believed to be largely episomal in nature such as adenoassociated virus (AAV) have also turned out to have this property. While advantageous in causing long-term expression, it also provides the potential for problems such as undesirable cellular transformation. The stable transformation of a patient's somatic cells makes it difficult to reverse the treatment regimen if undesirable side effects dictate that it should be stopped.
Problems have also been encountered in infecting certain cells. Retroviruses typically enter cells through cell surface receptors. If such receptors are not present on the cell, or not present in sufficient numbers, then infection may not be possible or may be inefficient. These viruses are also relatively labile in comparison to other viruses. Outbreaks of wild-type virus from recombinant virus-producing cell lines have also been reported, with the vector itself causing a disease. Moreover, many of these viruses only allow gene expression in dividing cells. Viral vectors based upon lentiviruses such as the Human Immunodeficiency Virus (HIV) do not have these problems, but concerns remain about using such viruses as vectors.
Other viruses have been proposed as vectors, such as herpes virus. In addition, various non-viral vectors such as ligand-DNA-conjugates have been proposed. Nevertheless, these approaches all pose certain problems. For example, a vector must not itself become a potential source for infection to the individual treated. However, as already mentioned, outbreaks of wild-type retroviruses have been reported in some cell lines. Similarly, the use of herpes virus as a vector has been found to result in persistence of the virus. Furthermore, many of these vectors can contain and express only a relatively small amount of genetic material. This is undesirable for numerous situations in which the ability to express multiple products is preferred.
Poxviruses have been used for many years as vectors, particularly with respect to providing a foreign antigen or self antigen to generate an immune response in a host. The advantages of the poxvirus vectors include: (i) ease of generation and production; (ii) the large size of the genome permitting insertion of multiple genes, (iii) efficient delivery of genes to multiple cell types, including antigen-presenting cells; (iv) high levels of protein expression; (v) optimal presentation of antigens to the immune system; (vi) the ability to elicit cell-mediated immune responses as well as antibody responses; and (vii) the long-term experience gained with using this vector in humans as a smallpox vaccine.
Attention has focused on orthopox such as the Wyeth strain, NYVAC (U.S. Pat. No. 5,364,773) and modified vaccinia Ankara (MVA). MVA was derived from the Ankara vaccinia strain CVA-1 which was used in the 1950s as a smallpox vaccine. In 1958, attenuation experiments were initiated in the laboratory of Dr. Anton Mayr (University of Munich) comprising terminal dilution of CVA in chicken embryo fibroblast (CEF) cells that ultimately resulted in over 500 passages. The resulting MVA is an attenuated, replication-defective virus, which is restricted to replication primarily in avian cells. Comparison of the MVA genome to its parent, CVA, revealed 6 major deletions of genomic DNA (deletion I, II, III, IV, V, and VI), totaling 31,000 basepairs. (Meyer et al., J. Gen. Virol. 72:1031-8 (1991)). MVA has been administered to numerous animal species, including monkeys, mice, swine, sheep, cattle, horses and elephants with no local or systemic adverse effects. Over 120,000 humans have been safely vaccinated with MVA by intradermal, subcutaneous or intramuscular injections. MVA has also been reported to be avirulent among normal and immunosuppressed animals (Mayr et al., Zentralb. Bakteriol. 167:375-90 (1978). Accordingly, in addition to utility as a smallpox vaccine, the more attenuated strains are attractive poxviruses for use as vectors for immune modulation and gene therapy.
Consequently, poxviruses can be genetically engineered to contain and express foreign DNA with or without impairing the ability of the virus to replicate. Such foreign DNA can encode protein antigens that induce an immune protection in a host inoculated with such recombinant poxvirus. For example, recombinant vaccinia viruses have been engineered to express immunizing antigens of herpes virus, hepatitis B, rabies, influenza, human immunodeficiency virus (HIV), and other viruses (Kieny et al., Nature 312:163-6 (1984); Smith et al., Nature 302: 490-5 (1983); Smith et al., Proc. Natl. Acad. Sci. USA 80:7155-9 (1983); Zagury et al., Nature 326:249-50 (1987); Cooney et al., Lancet 337:567-72 (1991); Graham et al., J. Infect. Dis. 166:24452 (1992). Recombinant vaccinia viruses have also been shown to elicit immune responses against influenza virus, dengue virus, respiratory syncytial virus, and human immunodeficiency virus. Poxviruses have also been used to generate immune reactions against tumor-associated antigens such as CEA, PSA and MUC. See also U.S. Pat. No. 5,656,465.
There remains a need for improved treatments for breast cancer. It would be particularly advantageous to develop a treatment system which could utilize the specific information regarding tumor associated antigens expressed in different breast cancers. Moreover, it would be useful to develop a system which could be adapted to treat all different types of breast cancers, including a system which could be adapted or tailored to treat a specific individual.